Liquid crystal composition and liquid crystal display device

ABSTRACT

The subject is to provide a liquid crystal composition that satisfies at least one characteristic of characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a suitable optical anisotropy, a negatively large dielectric anisotropy, a large specific resistance, a high stability to ultraviolet light and a high stability to heat, or that is suitably balanced regarding two characteristics thereof. The subject is to provide an AM device that has a short response time, a large voltage holding ratio, a large contrast ratio, a long service life and so forth. 
     The invention provides a liquid crystal composition having a negative dielectric anisotropy that includes a specific four-ring compound replaced by fluorine having a high maximum temperature as a first component, and a specific compound having a negatively large anisotropy as a second component, and provides a liquid crystal display device containing the composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal composition suitable for usein an active matrix (AM) device, and an AM device containing thecomposition. More specifically, the invention relates to a liquidcrystal composition having a negative dielectric anisotropy, and alsorelates to a device of an in plane switching (IPS) mode, a verticalalignment (VA) mode or a polymer sustained alignment (PSA) modecontaining the composition.

2. Related Art

In a liquid crystal display device, classification based on an operatingmode of liquid crystals includes phase change (PC), twisted nematic(TN), super twisted nematic (STN), electrically controlled birefringence(ECB), optically compensated bend (OCB), in-plane switching (IPS),vertical alignment (VA), polymer sustained alignment (PSA) and so forth.Classification based on a driving mode of the device includes a passivematrix (PM) and an active matrix (AM). PM is further classified intostatic, multiplex and so forth, and AM is classified into a thin filmtransistor (TFT), a metal insulator metal (MIM) and so forth. TFT isfurther classified into amorphous silicon and polycrystal silicon. Thelatter is classified into a high temperature type and a low temperaturetype according to a production process. Classification based on a lightsource includes a reflection type utilizing a natural light, atransmission type utilizing a backlight and a semi-transmission typeutilizing both the natural light and the backlight.

These devices contain a liquid crystal composition having suitablecharacteristics. The liquid crystal composition has a nematic phase.General characteristics of the composition should be improved to obtainan AM device having good general characteristics. Table 1 belowsummarizes a relationship between the general characteristics of thetwo. The general characteristics of the composition will be explainedfurther based on a commercially available AM device. A temperature rangeof a nematic phase relates to the temperature range in which the devicecan be used. A desirable maximum temperature of the nematic phase is 70°C. or more and a desirable minimum temperature is −10° C. or less. Theviscosity of the composition relates to the response time of the device.The rotation viscosity of the composition also relates to the responsetime of the device. A short response time is desirable for displaying amoving image. Accordingly, a small viscosity of the composition isdesirable. A small viscosity at a low temperature is more desirable.

TABLE 1 General Characteristics of Liquid Crystal Composition and AMDevice General Characteristics General Characteristics No of aComposition of an AM Device 1 Temperature range of a Usable temperaturerange nematic phase is wide is wide 2 Viscosity is small¹⁾ Response timeis short 3 Optical anisotropy is suitable Contrast ratio is large 4Dielectric anisotropy is Threshold voltage is low, electric positivelyor negatively power consumption is small, and large contrast ratio islarge 5 Specific resistance is large Voltage holding ratio is large, anda contrast ratio is large 6 It is stable to ultraviolet Service life islong light and heat ¹⁾A liquid crystal composition can be injected intoa cell in a shorter period of time.

The optical anisotropy of the composition relates to the contrast ratioof the device. A product (Δn×d) of the optical anisotropy (Δn) of thecomposition and the cell gap (d) of the device is designed to maximizethe contrast ratio. A suitable value of the product depends on the kindof operation mode. In a device having a VA mode, a suitable value is ina range of from 0.30 μm to 0.40 μm, and in a device having an IPS mode,a suitable value is in a range of from 0.20 μm to 0.30 μm. In this case,a composition having a large optical anisotropy is desirable for adevice having a small cell gap. A large dielectric anisotropy of thecomposition contributes to a low threshold voltage, a small electricpower consumption and a large contrast ratio of the device. Accordingly,a large dielectric anisotropy is desirable. A large specific resistanceof the composition contributes to a large voltage holding ratio and alarge contrast ratio of the device. Accordingly, a composition having alarge specific resistance is desirable at room temperature and also at ahigh temperature in the initial stage. A composition having a largespecific resistance is desirable at room temperature and also at a hightemperature after it has been used for a long time. A stability of thecomposition to an ultraviolet light and heat relates to a service lifeof the liquid crystal display device. In the case where the stability ishigh, the device has a long service life. These characteristics aredesirable for an AM device used in a liquid crystal projector, a liquidcrystal television and so forth.

In an AM device having a TN mode, a composition having a positivedielectric anisotropy is used. In an AM device having a VA mode, acomposition having a negative dielectric anisotropy is used. In an AMdevice having an IPS mode, a composition having a positive or negativedielectric anisotropy is used. In an AM device having a PSA mode, acomposition having a positive or negative dielectric anisotropy is used.

Examples of the liquid crystal composition having a negative dielectricanisotropy are disclosed in the following patent document No. 1. Theliquid crystal composition containing the compound including the firstcomponent is disclosed in the patent documents No. 2 and No. 3, whichrelate to the liquid crystal composition having a positive dielectricanisotropy. Examples of the liquid crystal composition containing thecompound of the first component are disclosed in the patent document No.3, however, the liquid crystal composition having a negative dielectricanisotropy is not disclosed.

-   No. 1: JP 2008-24815 A; No. 2: JP 2000-328060 A; No. 3: JP    2002-533526 A.

A desirable AM device has characteristics such as a wide usabletemperature range, a short response time, a high contrast ratio, a lowthreshold voltage, a large voltage holding ratio, a long service life,and so forth. A shorter response time is desirable by even onemillisecond. Thus, a composition having characteristics such as a highmaximum temperature of a nematic phase, a low minimum temperature of anematic phase, a low viscosity, a suitable optical anisotropy,positively or negatively a large dielectric anisotropy, a large specificresistance, a high stability to ultraviolet light, a high stability toheat, and so forth is especially desirable.

One of the advantages of the invention is to provide a liquid crystalcomposition that satisfies at least one of characteristic such as a highmaximum temperature of a nematic phase, a low minimum temperature of anematic phase, a small viscosity, a large optical anisotropy, a largedielectric anisotropy, a large specific resistance, a high stability toultraviolet light and a high stability to heat and so forth. Anotheradvantage of the invention is to provide a liquid crystal compositionthat is properly balanced regarding at least two of characteristics. Afurther advantage of the invention is to provide a liquid crystaldisplay device that contains the liquid crystal composition. Anadditional advantage of the invention is to provide a liquid crystalcomposition that has a large optical anisotropy, a large dielectricanisotropy, a high stability to ultraviolet light and so forth, and isto provide an AM device that has a short response time, a large voltageholding ratio, a large contrast ratio, a long service life and so forth.

SUMMARY OF THE INVENTION

The invention concerns a liquid crystal composition having a negativedielectric anisotropy that includes two components, wherein a firstcomponent is at least one compound selected from the group of compoundsrepresented by formulas (1), the second component is at least onecompound selected from the group of compounds represented by formula(2), and concerns a liquid crystal display device including thecomposition:

wherein R¹, R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine; R³ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons; one of X¹ and X² is oxygen andthe another is fluorine; ring A is independently 1,4-cyclohexylene,wherein one CH₂ group may be replaced by oxygen, or is 1,4-phenylene; Z¹is independently a single bond, ethylene, methyleneoxy or carbonyloxy;and m is 1 or 2.

The invention also concerns a liquid crystal display device thatincludes the liquid crystal composition, and so forth.

DETAILED DESCRIPTION OF THE INVENTION

The terms used in the specification and claims are defined as follows.The liquid crystal composition and the liquid crystal display device ofthe invention may occasionally be expressed simply as “the composition”and “the device,” respectively. A liquid crystal display device is ageneric term for a liquid crystal display panel and a liquid crystaldisplay module. The “liquid crystal compound” is a generic term for acompound having a liquid crystal phase such as a nematic phase, asmectic phase and so forth, and also for a compound having no liquidcrystal phase but being useful as a component of a composition. Theuseful compound contains, for example, a 6-membered ring such as1,4-cyclohexylene and 1,4-phenylene, and a rod like molecular structure.An optically active compound or a polymerizable compound mayoccasionally be added to the composition. Even in the case where thecompound is a liquid crystal compound, the compound is classified as anadditive herein. At least one compound selected from a group ofcompounds represented by formula (1) may be abbreviated to “the compound(1).” The “compound (1)” means one compound or two or more compoundsrepresented by formula (1). The same rules apply to compoundsrepresented by the other formulas. “Arbitrary” is used not only in caseswhen the position is arbitrary but also in cases when the number isarbitrary. However, it is not used in cases when the number is 0 (zero).

A higher limit of a temperature range of a nematic phase may beabbreviated to “a maximum temperature.” A lower limit of a temperaturerange of a nematic phase may be abbreviated to “a minimum temperature.”“A specific resistance is large” means that the composition has a largespecific resistance at room temperature and also nearly at the maximumtemperature of a nematic phase in the initial stage, the composition hasa large specific resistance at room temperature and also nearly at themaximum temperature of a nematic phase even after it has been used for along time. “A voltage holding ratio is large” means that a device has alarge voltage holding ratio at room temperature and also nearly at themaximum temperature of a nematic phase in the initial stage, the devicehas a large voltage holding ratio at room temperature and also nearly atthe maximum temperature of a nematic phase even after it has been usedfor a long time. In the description of the characteristics such asoptical anisotropy, the characteristics of the composition such as theoptical anisotropy and so forth are values measured in the methodsdisclosed in Examples. A first component means one compound, or two ormore compounds. “A ratio of the first component” means the percentage byweight (% by weight) of the first component based on the total weight ofliquid crystal composition. The same rule applies to the ratio of asecond component and so forth. A ratio of an additive mixed with thecomposition means the percentage by weight (% by weight) based on thetotal weight of liquid crystal composition.

The symbol R¹ is used for a plurality of compounds in the chemicalformulas of component compounds. The meanings of R¹ may be identical ordifferent in two arbitrary compounds among these. In one case, forexample, R¹ of the compound (1) is ethyl and R¹ of the compound (1-1) isethyl. In another case, R¹ of the compound (1) is ethyl and R¹ of thecompound (1-1) is propyl. This rule also applies to the symbols R², R³and so forth. CL in the chemical formulas is chlorine.

The invention has the following features.

1. The invention concerns a liquid crystal composition having a negativedielectric anisotropy that includes two components, wherein the firstcomponent is at least one compound selected from the group of compoundsrepresented by formulas (1), the second component is at least onecompound selected from the group of compounds represented by formulas(2):

wherein R¹, R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine; R³ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons; one of X¹ and X² is oxygenand the other is fluorine; ring A is independently 1,4-cyclohexylene or1,4-phenylene, arbitrary one —CH₂— in 1,4-cyclohexylene may be replacedby —O—; Z¹ is independently a single bond, ethylene, methyleneoxy orcarbonyloxy; and m is 1 or 2.

2. The liquid crystal composition according to item 1, wherein the ratioof the first component is from approximately 5% by weight toapproximately 30% by weight, and the ratio of the second component isfrom approximately 30% by weight to approximately 95% by weight, basedon the total weight of liquid crystal composition.

3. The liquid crystal composition according to any one of items 1 and 2,that in addition to a first, a second component, further includes atleast one compound selected from the group of compounds represented byformula (3) as a third component:

wherein R⁵ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁶ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; ring B andring C are each independently 1,4-cyclohexylene or 1,4-phenylene; Z² isa single bond, ethylene, methyleneoxy or carbonyloxy.

4. The liquid crystal composition according to item 3, wherein the firstcomponent is at least one compound selected from the group of compoundsrepresented by formula (1-1):

wherein R¹ and R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine.

5. In the above formula (1-1) of the first component, the liquid crystalcomposition according to item 4, wherein at least one of R¹ and R² isone compound selected from the group of compounds represented by alkenylhaving 2 to 12 carbons.

6. The liquid crystal composition according to any one of items 3 to 5,wherein the second component is at least one compound selected from thegroup of compounds represented by formula (2-1) to (2-7):

wherein R³ is independently alkyl having 1 to 12 carbons, alkenyl having2 to 12 carbons; R⁴ is independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, or alkenyl having 2 to 12 carbons.

7. The liquid crystal composition according to any one of items 3 to 6,wherein the third component is at least one compound selected from thegroup of compounds represented by formula (3-1) to (3-3):

wherein R⁵ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁶ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.

8. The liquid crystal composition according to item 7, wherein the thirdcomponent is at least one compound selected from the group of compoundsrepresented by formula (3-1).

9. The liquid crystal composition according to any one of items 3 to 8,wherein the first component is at least one compound selected from thegroup of compounds represented by formula (1-1), the second component isat least one compound selected from the group of compounds representedby formula (2-1) to (2-7), and the third component is at least onecompound selected from the group of compounds represented by formula(3-1).

10. The liquid crystal composition according to any one of items 3 to 9,wherein a ratio of the first component is from 5% by weight to 30% byweight, a ratio of the second component is from 30% by weight to 80% byweight, and a ratio of the third component is from 5% by weight to 50%by weight, based on the total weight of the liquid crystal composition.

11. The liquid crystal composition according to any one of items 3 and10, that in addition to a first, second, and third component and furtherincludes at least one compound selected from the group of compoundsrepresented by formula (4) as a fourth component:

wherein R⁷ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁸ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons; ring D and ring E are eachindependently 1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenyleneor 2,5-difluoro-1,4-phenylene; Z³ is a single bond, ethylene,methyleneoxy or carbonyloxy.

12. The liquid crystal composition according to item 11, wherein thefourth component is at least one compound selected from the group ofcompounds represented by the formula (4-1) to (4-3):

wherein R⁷ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁸ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons.

13. The liquid crystal composition according to item 12, wherein thefourth component is at least one compound selected from the group ofcompounds represented by the formula (4-1).

14. The liquid crystal composition according to any one of items 11 to13, wherein a ratio of the fourth component is from 5% by weight to 30%by weight, based on the total weight of the liquid crystal composition.

15. The liquid crystal composition according to any one of items 1 to14, wherein the composition has a maximum temperature of a nematic phaseof 70° C. or more, an optical anisotropy (25° C.) at a wavelength of 589nm of 0.08 or more, and a dielectric anisotropy (25° C.) at a frequencyof 1 kHz of −2 or less.

16. A liquid crystal device display that includes the liquid crystalcomposition according to any one of items 1 to 15.

17. The liquid crystal composition according to item 16, wherein theliquid crystal display device has an operation mode of a VA mode, an IPSmode or a PSA mode, and has a driving mode of an active matrix mode.

The invention further includes: (1) the composition described above,wherein the composition further contains an optically active compound;(2) the composition described above, wherein the composition furthercontains an additive, such as an antioxidant, an ultraviolet lightabsorbent, an antifoaming agent, a polymerizable compound, apolymerization initiator and so forth; (3) an AM device containing thecomposition described above; (4) a device having a TN, ECB, OCB, IPS, VAor PSA mode, containing the composition described above; (5) a device ofa transmission type, containing the composition described above; (6) useof the composition described above as a composition having a nematicphase; and (7) use as an optically active composition by adding anoptically active compound to the composition described above.

The composition of the invention will be explained in the followingorder. First, the constitution of component compounds in the compositionwill be explained. Second, the main characteristics of the componentcompounds and the main effects of the compounds on the composition willbe explained. Third, combinations of components in the composition,desirable ratios of the component compounds and the basis thereof willbe explained. Fourth, a desirable embodiment of the component compoundswill be explained. Fifth, examples of the component compound will beshown. Sixth, additives that may be added to the composition will beexplained. Seventh, the preparation methods of the component compoundwill be explained. Lastly, use of the composition will be explained.

First, the constitution of component compounds in the composition willbe explained. The composition of the invention is classified into thecomposition A and the composition B. The composition A may furthercontain other compounds such as another liquid crystal compound, anadditive, an impurity, and so forth. “Another liquid crystal compound”is different from the compound (1), the compound (2), the compound (3),and the compound (4). Such a liquid crystal compound is mixed with thecomposition for the purpose of adjusting the characteristics of thecomposition. Among the other liquid crystal compounds, an amount of acyano compound is desirably small from the viewpoint of stability toheat or ultraviolet light. The more desirable amount of a cyano compoundis 0% by weight. The additive includes an optically active compound, anantioxidant, an ultraviolet light absorbent, a coloring matter, anantifoaming agent, a polymerizable compound, a polymerization initiatorand so forth. The impurity is a compound and so forth contaminated inthe process such as the synthesis of a component compound and so forth.Even when the compound is a liquid crystal compound, it is classifiedinto an impurity herein.

The composition B essentially consists of the compounds selected fromthe compound (1), the compound (2), the compound (3) and the compound(4). The term “essentially” means that the composition does not containa liquid crystal compound that is different from these compounds, exceptfor the additive and the impurity. The components of the composition Bare fewer than those of the composition A. The composition B ispreferable to the composition A from the viewpoint of cost reduction.The composition A is preferable to the composition B, becausecharacteristics of the composition A can be further adjusted by mixingother liquid crystal compounds.

Second, the main characteristics of the component compounds and the maineffects of the compounds on the composition will be explained. The maincharacteristics of the component compounds are summarized in Table 2. InTable 2, the symbol L represents large or high, the symbol M representsa middle degree, and the symbol S represents small or low. The symbolsL, M and S are classification based on qualitative comparison among thecomponent compounds. 0 (zero) of dielectric anisotropy means that “avalue of dielectric anisotropy is not positively or negatively large andis nearly zero.”

TABLE 2 Characteristics of Compounds Compound (1) (2) (3) (4) Maximumtemperature L S-M S M Viscosity M M-L S M Optical anisotropy M S-M S-MM-L Dielectric anisotropy 0 L 0 0 Specific resistance L L L L 1) Thevalue of dielectric anisotropy is negative, and the symbol indicates theabsolute value.

The main effects of the component compounds on the characteristics ofthe composition upon mixing the component compounds in the compositionare as follows. The compound (1) increases the maximum temperature. Thecompound (2) increases the absolute value of the dielectric anisotropy.The compound (3) decreases the viscosity. The compound (4) adjusts theoptical anisotropy into the suitable value and decreases the minimumtemperature.

Third, combinations of components in the composition, desirable ratiosof the component compounds and the basis thereof will be explained.Example of the combinations of the components in the composition isfirst component+second component, first component+second component+thirdcomponent, first component+second component+third component+fourthcomponent.

Desirable combinations of components in the composition are firstcomponent+second component for increasing the absolute value ofdielectric anisotropy, first component+second component+third componentand first component+second component+third component+fourth componentfor decreasing viscosity.

A desirable ratio of the first component is 5% by weight or more forincreasing the maximum temperature, and is 30% by weight or less fordecreasing the minimum temperature. A more desirable ratio is from 5% byweight to 25% by weight. A particularly desirable ratio is from 5% byweight to 20% by weight.

A desirable ratio of the second component is 30% by weight or more forincreasing the absolute value of dielectric anisotropy, and is 95% byweight or less for decreasing the minimum temperature. A more desirableratio is from 30% by weight to 80% by weight. A particularly desirableratio is from 40% by weight to 70% by weight.

A desirable ratio of the third component is 5% by weight or more fordecreasing the viscosity, and is 50% by weight or less for increasingthe absolute value of the dielectric anisotropy. A more desirable ratiois from 5% by weight to 40% by weight. A particularly desirable ratio isfrom 10% by weight to 30% by weight.

A desirable ratio of the fourth component is 5% by weight or more fordecreasing the minimum temperature, and is 30% by weight or less forincreasing the absolute value of dielectric anisotropy. A more desirableratio is from 5% by weight to 15% by weight. A particularly desirableratio is from 5% by weight to 10% by weight.

Fourth, a desirable embodiment of the component compound will beexplained. R¹ and R² are each independently alkyl having 1 to 12carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbonsor alkenyl having 2 to 12 carbons in which arbitrary hydrogen isreplaced by fluorine; R³, R⁵ and R⁷ are each independently alkyl having1 to 12 carbons alkenyl having 2 to 12 carbons; R⁴ and R⁸ are eachindependently alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; R⁶ is each independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons, alkenyl having 2 to 12 carbons in whicharbitrary hydrogen is replaced by fluorine.

Desirable R¹ and R² are each independently alkyl having 1 to 12 carbonsor alkenyl having 2 to 12 carbons for decreasing the minimumtemperature. At least one of more desirable R¹ and R² is alkenyl having2 to 12 carbons. Desirable R³ is independently alkyl having 1 to 12carbons for increasing the stability to ultraviolet light or heat.Desirable R⁴ is independently alkoxy having 1 to 12 carbons forincreasing the absolute value of dielectric anisotropy. Desirable R⁵,R⁶, R⁷ and R⁸ are each independently alkyl having 1 to 12 carbons forincreasing the stability to ultraviolet light or heat, or is alkenylhaving 2 to 12 carbons for decreasing the minimum temperature.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,or octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl or heptylfor decreasing a viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy, or heptyloxy. More desirable alkoxy is methoxy or ethoxy fordecreasing a viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl. More desirablealkenyl is vinyl, 1-propenyl, 3-butenyl, or 3-pentenyl for decreasing aviscosity. A desirable configuration of —CH═CH— in these alkenyl dependson the position of a double bond. Trans is desirable in the alkenyl suchas 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, and3-hexenyl for decreasing the viscosity. Cis desirable in the alkenylsuch as 2-butenyl, 2-pentenyl and 2-hexenyl. In these alkenyls, straightchained alkenyl is preferable to branched alkenyl.

Preferred examples of alkenyl in which arbitrary hydrogen is replaced byfluorine include 2,2-difluorovinyl, 3,3-difluoro-2-propenyl,4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl and6,6-difluoro-5-hexenyl. More preferred examples thereof include2,2-difluorovinyl and 4,4-difluoro-3-butenyl for decreasing theviscosity.

Ring A is independently 1,4-cyclohexylene, in which one —CH₂— may bereplaced by oxygen, or is 1,4-phenylene. Ring B and C are eachindependently 1,4-cyclohexylene or 1,4-phenylene. Two rings A may besame or different from each other when m is 2. Desirable ring A isindependently 1,4-cyclohexylene for decreasing the viscosity. Ring D andE are each independently 1,4-cyclohexylene, or 1,4-phenylene,3-fluoro-1,4-phenylene or 2,5-difluoro-1,4-phenylene. When the rings are3-fluoro-1,4-phenylene, the directions of the rings are not limited.Desirable ring C, ring D and ring E are each independently1,4-cyclohexylene for decreasing the viscosity, or is 1,4-phenylene forincreasing the optical anisotropy.

One of X¹ and X² is hydrogen, and the other is fluorine. In desirablecombinations of X¹ and X², X¹ is hydrogen and X² is fluorine fordecreasing the minimum temperature.

Z¹ is independently a single bond, ethylene, methyleneoxy orcarbonyloxy. Z¹ may be same or different from each other, when m is 2.Desirable Z¹ is a single bond or ethylene for decreasing a viscosity, oris methyleneoxy for increasing the absolute value of dielectricanisotropy. Z² is independently a single bond, ethylene, vinylene,methyleneoxy or carbonyloxy.

Desirable Z² is a single bond for decreasing a viscosity. Z³ is a singlebond, ethylene, vinylene, methyleneoxy or carbonyloxy. Desirable Z³ is asingle bond for decreasing a viscosity.

m is 1 or 2. Desirable m is 1 for decreasing the minimum temperature,and is 2 for increasing the maximum temperature

Fifth, examples of the component compounds will be shown. In thedesirable compounds described below, R⁹ is independently alkenyl having1 to 12 carbons. R¹⁰ is independently straight chained alkyl having 1 to12 carbons or straight chained alkoxy having 1 to 12 carbons. In thesedesirable compounds, trans is preferable to cis for the configuration of1,4-cyclohexylene for increasing the maximum temperature.

Desirable compounds (1) are the compounds (1-1), (1-2), and thecompounds (1-1-1) to (1-1-3). More desirable compound (1) is thecompound (1-1). Particularly more desirable compounds (1) are thecompounds (1-1-1) to (1-1-2). Desirable compounds (2) are the compound(2-1) to (2-7). More desirable compounds (2) are the compound (2-1),(2-2), (2-4) and (2-7). Desirable compounds (3) are the compounds (3-1)to (3-3). More desirable compound (3) is the compound (3-1). Desirablecompounds (4) are the compounds (4-1) to (4-3). More desirable compound(4) is the compound (4-1).

Sixth, additives capable of being mixed with the composition will beexplained. The additives include an optically active compound, anantioxidant, an ultraviolet light absorbent, a coloring matter, anantifoaming agent, a polymerizable compound, a polymerization initiatorand so forth. An optically active compound is mixed in the compositionfor inducing a helical structure of liquid crystal to provide a twistangle. Examples of the optically active compound include the compounds(5-1) to (5-4) below. A desirable ratio of the optically active compoundis 5% by weight or less, and a more desirable ratio thereof ranges from0.01% by weight to 2% by weight.

An antioxidant is mixed with the composition in order to avoid adecrease in specific resistance caused by heating in the air or tomaintain a large voltage holding ratio at room temperature and alsonearly at the maximum temperature even after the device has been usedfor a long time.

Preferred examples of the antioxidant include the compound (6):

wherein n is an integer from 1 to 9. In the compound (6), desirable nare 1, 3, 5, 7, or 9. More desirable n are 1 or 7. When n is 1, thecompound (6) has a large volatility, and is effective in preventing thedecrease of specific resistance caused by heating in the air. When n is7, the compound (6) has a small volatility, and is effective inmaintaining a large voltage holding ratio at room temperature and alsonearly at a high temperature even after the device has been used for along time. A desirable ratio of the antioxidant is 50 ppm or more inorder to obtain the advantages thereof and is 600 ppm or less in orderto prevent the decrease of maximum temperature and to prevent theincrease of minimum temperature. A more desirable ratio is from 100 ppmto 300 ppm.

Preferred examples of the ultraviolet light absorbent include abenzophenone derivative, a benzoate derivative and a triazolederivative. A light stabilizer having steric hindrance such as an amineis also desirable. A desirable ratio of the absorbent and the stabilizeris 50 ppm or more for obtaining the advantages thereof and is 10,000 ppmor less for preventing the decreasing of maximum temperature andpreventing the increase of minimum temperature. A more desirable ratiothereof ranges from 100 ppm to 10,000 ppm.

A dichroic dye such as an azo dye or an anthraquinone dye is mixed withthe composition to suit for a device of a guest host (GH) mode. Adesirable ratio of the dye ranges from 0.01% by weight to 10% by weight.An antifoaming agent such as dimethyl silicone oil or methylphenylsilicone oil is mixed with the composition for preventing foaming fromoccurring. A desirable ratio of the antifoaming agent is 1 ppm or morefor obtaining the advantages thereof and is 1,000 ppm or less forpreventing display failure from occurring. A more desirable ratiothereof ranges from 1 ppm to 500 ppm.

A polymerizable compound is mixed with the composition for applying thecomposition to a device having a PSA (polymer sustained alignment) mode.Preferred examples of the polymerizable compound include compoundshaving a polymerizable group, such as acrylate, methacrylate, vinyl,vinyloxy, propenyl ether, vinylketone, epoxy such as oxirane, oxetane,and so forth. Particularly preferred examples thereof includederivatives of acrylate or methacrylate. A desirable ratio of thepolymerizable group is from 0.05% by weight or more for obtaining theadvantages thereof, and is 10% by weight or less for preventing displayfailure from occurring. A more desirable ratio is from 0.1% by weight to2% by weight. The polymerizable compound is polymerized preferably inthe presence of a suitable initiator, such as a photopolymerizationinitiator and so forth, under radiation of ultraviolet light. Suitableconditions for polymerization and a suitable type and a suitable amountof the initiator have been known by a skilled person in the art and aredisclosed in literatures. Examples of the photopolymerization initiatorsuitable for radical polymerization include Irgacure 651 (trade name),Irgacure 184 (trade name) and Darocure 1173 (trade name), all producedby Ciba Japan K.K. The polymerizable compound preferably contains aphotopolymerization initiator in an amount of from 0.1% by weight to 5%by weight, and particularly preferably contains a photopolymerizationinitiator in an amount of from 1% by weight to 3% by weight.

Seventh, the preparation methods of the component compounds will beexplained. These compounds can be prepared by known methods. Thepreparation method will be exemplified below. The compounds (2-1) and(2-4) are synthesized by the method disclosed in JP H2-503441 A/1990 andJP 2000-053602 A. The compound (2-7) is synthesized by the methoddisclosed in JP 557-114532A. The compounds (3-1) and (3-4) aresynthesized by the method disclosed in JP H4-30382 A. The antioxidant iscommercially available. The compound (6), wherein n is 1, is available,for example, from Sigma-Aldrich, Inc. The compound (6), wherein n is 7,and so forth are prepared by the method disclosed in U.S. Pat. No.3,660,505.

The compounds for which preparation methods were not described above canbe prepared according to the methods described in Organic Syntheses(John Wiley & Sons, Inc.), Organic Reactions (John Wiley & Sons, Inc.),Comprehensive Organic Synthesis (Pergamon Press), New ExperimentalChemistry Course (Shin Jikken Kagaku Kouza) (Maruzen, Inc.), and soforth. The composition is prepared according to known methods using thecompounds thus obtained. For example, the component compounds are mixedand dissolved in each other by heating.

Last, use of the composition will be explained. The compositions of theinvention mainly have a minimum temperature of −10° C. or less, amaximum temperature of 70° C. or more, and an optical anisotropy of 0.07to 0.20. The device containing the composition has a large voltageholding ratio. The composition is suitable for an AM device. Thecomposition is suitable especially for an AM device of a transmissiontype. The composition having an optical anisotropy of 0.08 to 0.25 andfurther having an optical anisotropy of 0.10 to 0.30 may be prepared bycontrolling ratios of the component compounds or by mixing other liquidcrystal compounds. The composition can be used as a composition having anematic phase and as an optically active composition by adding anoptically active compound.

The composition can be used for an AM device. It can be also used for aPM device. The composition can be also used for an AM device and a PMdevice having a mode such as PC, TN, STN, ECB, OCB, IPS, VA, PSA and soforth. It is desirable to use the composition for an AM device having aTN, OCB or IPS mode. These devices may be of a reflection type, atransmission type or a semi-transmission type. It is desirable to usethe composition for a device of a transmission type. It can be used foran amorphous silicon-TFT device or a polycrystal silicon-TFT device. Thecomposition is also usable for a nematic curvilinear aligned phase(NCAP) device prepared by microcapsulating the composition, and for apolymer dispersed (PD) device in which a three dimensional net-workpolymer is formed in the composition.

EXAMPLES

A sample of the liquid crystal compound for measuring characteristicsincludes two cases, i.e., the case where the compound itself is used asa sample, and the case where the compound is mixed with mother liquidcrystals to prepare a sample.

In the later case where a sample is prepared by mixing the compound withmother liquid crystals, the measurement is carried out in the followingmanner. A sample was produced by mixing 15% by weight of the compoundand 85% by weight of mother liquid crystals. A value of characteristicsof the compound was calculated by extrapolating from a value obtained bymeasurement.Extrapolated Value=(100×(measured value of sample)−(percentage by weightof mother liquid crystals)×(value measured for mother liquidcrystals))/(percentage by weight of liquid crystal compound)

In the case where a smectic phase was exhibited at 25° C. or crystalswere deposited at 25° C. at this ratio of the liquid crystal compoundand the mother liquid crystals, the ratio of the compound and the motherliquid crystals was changed step by step in the order of (10% byweight/90% by weight), (5% by weight/95% by weight), (1% by weight/99%by weight), respectively. The value of characteristics of the sample wasmeasured at a ratio where a smectic phase or crystals were not depositedat 25° C., and an extrapolated value was obtained by the aforementionedequation, which was designated as a value of characteristics of theliquid crystal compound.

While there are various kinds of mother liquid crystals for theaforementioned measurement, the composition of the mother liquidcrystals was as follows, for example.

Mother Liquid Crystals is:

Measurement of the characteristics was carried out according to thefollowing methods. Most methods are described in the Standard ofElectric Industries Association of Japan, EIAJ ED-2521 A or those withsome modifications.

Maximum Temperature of Nematic Phase (NI; ° C.):

A sample was placed on a hot plate in a melting point apparatus equippedwith a polarizing microscope, and while heating at the rate of 1° C. perminute, was observed with the polarizing microscope. A temperature wherea part of the sample is changed from a nematic phase to an isotropicliquid was measured. The maximum temperature of a nematic phase may beabbreviated to “a maximum temperature” in some cases.

Minimum Temperature of Nematic Phase (Tc; ° C.):

The glass bottles containing a sample having a nematic phase were storedin a freezer at 0° C., −10° C., −20° C., −30° C., −40° C. for aprescribed period of time. For example, a sample at −20° C. remains anematic phase. When a sample changes to crystal of smectic phase at 30°C. Tc is expressed as −20° C. The minimum temperature of a nematic phasemay be abbreviated to “a minimum temperature”.

Viscosity (η; Measured at 20° C.; mPa·s):

The viscosity was measured by means of an E-type viscometer.

Viscosity (rotational viscosity; γ1; measured at 25° C.; mPa·s):Measurement was carried out according to the method described in M.Imai, et al., Molecular Crystals and Liquid Crystals, Vol. 259, 37(1995). A sample was poured into a TN device having a twist angle of 0degrees and the distance between two glass substrates (cell gap) of 5μm. The TN device was impressed with a voltage stepwise with anincrement of 0.5 volt in the range of 16 to 19.5 volts. After a periodof 0.2 second without impressed no impress of voltage, voltage impresswas repeated under the conditions of with only one rectangular wave(rectangular pulse; of 0.2 second) and no impress of voltage impressed(2 seconds). The peak current and the peak time of the transient currentgenerated by the voltage impressed were measured. The value ofrotational viscosity was obtained from the measured values and thecalculating equation (8) in page 40 of the paper presented by M. Imai,et al. The value of dielectric anisotropy necessary for this calculationwas obtained by use of the device that had been used for the presentmeasurement of rotational viscosity, according to the method that willbe described below.Optical Anisotropy (Refractive Index Anisotropy; Δn; Measured at 25°C.):

Measurement was carried out with an Abbe refractometer mounting apolarizing plate on an ocular using a light at a wavelength of 589 nm.The surface of a main prism was rubbed in one direction, and then asample was dropped on the main prism. Refractive index (n∥) was measuredwhen the direction of a polarized light was parallel to that of therubbing. Refractive index (n⊥) was measured when the direction of apolarized light was perpendicular to that of the rubbing. A value ofoptical anisotropy was calculated from the equation: Δn=n∥−n⊥.

Dielectric Anisotropy (Δ∈; Measured at 25° C.):

A sample was put in a TN device having a distance between two glasssubstrates (cell gap) of 9 μm and a twist angle of 80°. Sine waves (10V, 1 kHz) were applied to the device, and a dielectric constant (∈∥) ina major axis direction of a liquid crystal molecule was measured after 2seconds. Sine waves (0.5 V, 1 kHz) were applied to the device, and adielectric constant (∈⊥) in a minor axis direction of a liquid crystalmolecule was measured after 2 seconds. A value of a dielectricanisotropy was calculated from the equation: Δ∈=∈∥−∈⊥.

Threshold Voltage (Vth; Measured at 25° C.; V):

Measurement was carried out with an LCD Evaluation System Model LCD-5100made by Otsuka Electronics Co., Ltd. The light source was a halogenlamp. A sample was poured into a VA device of a normally black mode, andthe device was sealed with UV curable adhesive. Voltage to be applied tothe device (60 Hz, rectangular waves) was stepwise increased by 0.02Vstarting from 0V up to 20V. During the stepwise increasing, the devicewas irradiated with light in a perpendicular direction, and an amount ofthe light passing through the device was measured. Voltage-transmissioncurve was prepared, in which a maximum amount of a light corresponded to100% transmittance, and a minimum amount of a light corresponded to 0%transmittance. Threshold voltage is a value at 10% transmittance.

Voltage Holding Ratio (VHR-1; Measured at 25° C.; %):

A TN device used for measurement has a polyimide-alignment film and thecell gap between two glass plates is 5 μm. A sample was poured into thedevice, and then the device was sealed with an adhesive which ispolymerized by the irradiation of an ultraviolet light. The TN devicewas applied and charged with pulse voltage (60 microseconds at 5V).Decreasing voltage was measured for 16.7 milliseconds with High SpeedVoltmeter and the area A between a voltage curve and a horizontal axisin a unit cycle was obtained. The area B was an area without decreasing.Voltage holding ratio is a percentage of the area A to the area B.

Voltage Holding Ratio (VHR-2; Measured at 80° C.; %):

A TN device used for measurement has a polyimide-alignment film and thecell gap between two glass plates is 5 μm. A sample was poured into thedevice, and then the device was sealed with an adhesive which ispolymerized by the irradiation of an ultraviolet light. The TN devicewas applied and charged with pulse voltage (60 microseconds at 5V).Decreasing voltage was measured for 16.7 milliseconds with High SpeedVoltmeter and the area A between a voltage curve and a horizontal axisin a unit cycle was obtained. The area B was an area without decreasing.Voltage holding ratio is a percentage of the area A to the area B.

Voltage Holding Ratio (VHR-3; Measured at 25° C.; %):

A voltage holding ratio was measured after irradiating with ultravioletlight to evaluate stability to ultraviolet light. A composition havinglarge VHR-3 has a large stability to ultraviolet light. A TN device usedfor measurement has a polyimide-alignment film and the cell gap is 5 μm.A sample was poured into the device, and then the device was irradiatedwith light for 20 minutes. The light source was a superhigh voltagemercury lamp USH-500D (produced by Ushio, Inc.), and the distancebetween the device and the light source is 20 cm. In measurement ofVHR-3, a decreasing voltage is measured for 16.7 milliseconds. VHR-3 isdesirably 90% or more, and more desirably 95% or more.

Voltage Holding Ratio (VHR-4; Measured at 25° C.; %):

A voltage holding ratio was measured after heating a TN device having asample poured therein in a constant-temperature bath at 80° C. for 500hours to evaluate stability to heat. A composition having large VHR-4has a large stability to heat. In measurement of VHR-4, a decreasingvoltage is measured for 16.7 milliseconds.

Response Time (τ; Measured at 25° C.; Millisecond):

Measurement was carried out with an LCD Evaluation System Model LCD-5100made by Otsuka Electronics Co., Ltd. Light source is a halogen lamp.Low-pass filter was set at 5 kHz. A sample was poured into a VA deviceof a normally black mode, in which a rubbing direction is anti-parallel.The device was sealed with UV curable adhesive, rectangle waves (60 Hz,10V, 0.5 seconds) were applied thereto. During application, the devicewas irradiated with light in a perpendicular direction, and an amount ofthe light passing through the device was measured. A maximum amount of alight corresponds to 100% transmittance, and a minimum amount of a lightcorresponds to 0% transmission. Fall time (τr; millisecond) is a periodof time required for the change in transmittance from 90% to 10%.

Specific Resistance (ρ; Measured at 25° C.; Ωcm):

1.0 ml of a sample was charged in a vessel equipped with electrodes. Adirect current voltage of 10V was applied to the vessel, and afterlapsing 10 second from the application of voltage, the direct electriccurrent was measured. The specific resistance was calculated by theequation:(specific resistance)=((voltage)×(electric capacity of vessel))/((directcurrent)×(dielectric constant of vacuum)).Gas Chromatographic Analysis:

A Gas Chromatograph Model GC-14B made by Shimadzu Corporation was usedfor measurement. The carrier gas was helium (2 milliliters per minute).The evaporator and the detector (FID) were set up at 280° C. and 300°C., respectively. A capillary column DB-1 (length 30 meters, bore 0.32millimeter, film thickness 0.25 μm, dimethylpolysiloxane as thestationary phase, non-polar) made by Agilent Technologies, Inc. was usedfor the separation of component compounds. After the column had beenkept at 200° C. for 2 minutes, it was further heated to 280° C. at therate of 5° C. per minute. A sample was dissolved in acetone (0.1% byweight) and 1 microliter of the solution was injected into theevaporator. A recorder used was a Model C-R5A Chromatopac Integratormade by Shimadzu Corporation or its equivalent. A gas chromatogramobtained showed the retention time of peaks and the peak areascorresponding to the component compounds.

Solvents for diluting the sample may also be chloroform, hexane, and soforth. The following capillary columns may also be used in order toseparate the component compounds: HP-1 made by Agilent Technologies Inc.(length 30 meters, bore 0.32 millimeter, film thickness 0.25 μm), Rtx-1made by Restek Corporation (length 30 meters, bore 0.32 millimeter, filmthickness 0.25 μm), and BP-1 made by SGE International Pty. Ltd. (length30 meters, bore 0.32 millimeter, film thickness 0.25 μm). A capillarycolumn CBP1-M50-025 (length 50 meters, bore 0.25 millimeter, filmthickness 0.25 μm) made by Shimadzu Corporation may also be used for thepurpose of avoiding an overlap of peaks of the compounds.

The ratio of the liquid crystal compound included in the composition maybe calculated according to the following method. The liquid crystalcompounds are detected by use of a gas chromatograph. The ratio of peakareas in the gas chromatogram corresponds to the ratio (in moles) of theliquid crystal compounds. When the capillary columns described above areused, the correction coefficient of respective liquid crystal compoundsmay be regarded as 1 (one). Accordingly, the ratio (% by weight) of theliquid crystal compound can be calculated from the ratio of peak areas.

The invention will be explained in detail by way of Examples. Theinvention is not limited by the Examples described below. The compoundsdescribed in the Comparative Examples and the Examples are expressed bythe symbols according to the definition in Table 3. In Table 3, theconfiguration of 1,4-cyclohexylene is trans. The parenthesized numbernext to the symbolized compounds in the Examples corresponds to thenumber of the desirable compound. The symbol (−) means other liquidcrystal compound. A ratio (percentage) of a liquid crystal compound ispercentage by weight (% by weight) based on the total weight of liquidcrystal compounds, and the liquid crystal compositions further containimpurities. Last, the characteristics of the composition are summarized.

TABLE 3 Method of Description of Compound using Symbols.

1) Left Terminal Group R— Symbol C_(n)H_(2n+1)— n- C_(n)H_(2n+1)O— nO—C_(m)H_(2m+1)OC_(n)H_(2n)— mOn— CH₂═CH— V— C_(n)H_(2n+1)—CH═CH— nV—CH₂═CH—C_(n)H_(2n)— Vn— C_(m)H_(2m+1)—CH═CH—C_(n)H_(2n)— mVn—CH₂═CH—C₂H₄—CH═CH—C₂H₄— V2V2— CF₂═CH— VFF— CF₂═CH—(CH₂)₂— VFF2— 2) RightTerminal Group —R′ Symbol —C_(n)H_(2n+1) -n —OC_(n)H_(2n+1) —On —F —F—Cl —CL —OCF₃ —OCF3 —OCF₂CFHCF₃ —OCF2CFHCF3 —CH═CH₂ —V—CH═CH—C_(n)H_(2n+1) —Vn —C_(n)H_(2n)—CH═CH₂ —nV —CH═CF₂ —VFF 3) Bondinggroup —Zn— Symbol —C₂H₄— 2 —COO— E —CH═CH— V —C≡C— T —CH₂O— 1O —OCH₂— O14) Ring Structure —An— Symbol

H

B

B(F)

B(2F)

B(2F,3F)

B(2F,3CL)

B(2F,5F)

Cro(7F,8F) 5) Example of Description Example 1 3-HB(F)HH-5

Example 2 1V2—H2B(2F,3F)—O2

Example 3 4-HH—V

Example 4 3-HH1OCro(7F,8F)-5

Comparative Example 1

The composition is the liquid crystal composition having a negativedielectric anisotropy which doesn't contain the first component of theinvention. The composition of Comparative Example 1 is the liquidcrystal composition which is replaced by the compound similar to fourring compound in which the first component of composition of Example 1herein is not replaced by fluorine. The composition was prepared andmeasured by the above described method. The component andcharacteristics of the composition are as follows.

2-HBHH-3 (—) 8% 3-H2B(2F,3F)-O2 (2-2) 17% 5-H2B(2F,3F)-O2 (2-2) 17%2-HBB(2F,3F)-O2 (2-7) 3% 3-HBB(2F,3F)-O2 (2-7) 10% 5-HBB(2F,3F)-O2 (2-7)10% 2-HH-3 (3-1) 25% V-HHB-1 (4-1) 4% 3-HHB(2F,3CL)-O2 (—) 3%5-HHB(2F,3CL)-O2 (—) 3%

NI=79.9° C.; Tc≦0° C.; Δn=0.092; η=21.7 mPa·s; Δ∈=−2.7; Vth=2.40 V.

Example 1

The composition of Example 1 is the liquid crystal composition in whichfour ring compound included in Comparative Example 1 is replaced by thecompounds (1-1-3) of the first component.

3-HB(F)HH-5 (1-1-3) 8% 3-H2B(2F,3F)-O2 (2-2) 17% 5-H2B(2F,3F)-O2 (2-2)17% 2-HBB(2F,3F)-O2 (2-7) 3% 3-HBB(2F,3F)-O2 (2-7) 10% 5-HBB(2F,3F)-O2(2-7) 10% 2-HH-3 (3-1) 25% V-HHB-1 (4-1) 4% 3-HHB(2F,3CL)-O2 (—) 3%5-HHB(2F,3CL)-O2 (—) 3%

NI=79.8° C.; Tc≦−20° C.; Δn=0.092; η=20.5 mPa·s; Δ∈=−3.1; Vth=2.32 V.

The composition of Example 1 has a lower minimum temperature of nematicphase, a smaller viscosity and a negatively larger dielectric anisotropythan those of Comparative Example 1.

Example 2

3-HB(F)HH-5 (1-1-3) 10% 3-H2B(2F,3F)-O2 (2-2) 20% 5-H2B(2F,3F)-O2 (2-2)21% 3-HH-V (3-1) 19% V-HHB-1 (4-1) 5% 3-HHB(2F,3CL)-O2 (—) 4%5-HHB(2F,3CL)-O2 (—) 5% 3-HBB(2F,3CL)-O2 (—) 8% 5-HBB(2F,3CL)-O2 (—) 8%

NI=81.2° C.; Tc≦−30° C.; Δn=0.091; Δ∈=−3.3; Vth=2.32 V.

Example 3

3-HB(F)HH-2 (1-1-3) 3% 3-HB(F)HH-5 (1-1-3) 6% 5-HB(F)HH-2 (1-1-3) 3%5-HB(F)HH-5 (1-1-3) 4% 3-H2B(2F,3F)-O2 (2-2) 26% 5-H2B(2F,3F)-O2 (2-2)27% 2-HBB(2F,3F)-O2 (2-7) 3% 3-HBB(2F,3F)-O2 (2-7) 9% 5-HBB(2F,3F)-O2(2-7) 9% 3-HH1OCro(7F,8F)-5 (—) 2% 3-HHB(2F,3CL)-O2 (—) 3%5-HHB(2F,3CL)-O2 (—) 3% 5-HBB(F)B-2 (—) 2%

NI=88.2° C.; Tc≦−20° C.; Δn=0.111; η=47.7 mPa·s; Δ∈=−5.2; Vth=2.13 V.

Example 4

3-HB(F)HH-V (1-1-2) 4% 5-HB(F)HH-V (1-1-2) 10% 5-HB(F)HH-V1 (1-1-2) 3%3-H2B(2F,3F)-O2 (2-2) 24% 5-H2B(2F,3F)-O2 (2-2) 27% V2-HHB(2F,3F)-O2(2-4) 6% 3-HHB(2F,3F)-O2 (2-4) 4% 2-HBB(2F,3F)-O2 (2-7) 3%3-HBB(2F,3F)-O2 (2-7) 10% 5-HBB(2F,3F)-O2 (2-7) 9%

NI=89.9° C.; Tc≦−20° C.; Δn=0.108; η=44.7 mPa·x; Δ∈=−5.2; Vth=2.13 V;VHR-1=99.2%; VHR-2=94.7%.

Example 5

3-HB(F)HH-5 (1-1-3) 15% V-HB(2F,3F)-O1 (2-1) 10% V-HB(2F,3F)-O2 (2-1)20% V-HB(2F,3F)-O4 (2-1) 15% 2-HBB(2F,3F)-O2 (2-7) 5% 3-HBB(2F,3F)-O2(2-7) 9% 5-HBB(2F,3F)-O2 (2-7) 10% 2-HH-3 (3-1) 6% 3-HHB-1 (4-1) 5%3-HHB-3 (4-1) 3% 2-HHB(2F,3CL)-O2 (—) 2%

NI=78.2° C.; Tc≦−20° C.; Δn=0.103; Δ∈−4.4; Vth=1.79 V.

Example 6

3-HB(F)HH-5 (1-1-3) 9% V-HB(2F,3F)-O2 (2-1) 17% V-HB(2F,3F)-O4 (2-1) 9%2-HBB(2F,3F)-O2 (2-7) 3% 3-HBB(2F,3F)-O2 (2-7) 10% 5-HBB(2F,3F)-O2 (2-7)10% 2-HH-3 (3-1) 29% 3-HHB-1 (4-1) 6% 2-HHB(2F,3CL)-O2 (—) 2%3-HHB(2F,3CL)-O2 (—) 3% 5-HHB(2F,3CL)-O2 (—) 2%

NI=80.4° C.; Tc≦−20° C.; Δn=0.090; η=18.0 mPa·s; Δ∈×−2.9; Vth=2.19 V.

Example 7

3-HB(F)HH-5 (1-1-3) 10% V-HB(2F,3F)-O2 (2-1) 25% 2-HBB(2F,3F)-O2 (2-7)5% 3-HBB(2F,3F)-O2 (2-7) 11% 5-HBB(2F,3F)-O2 (2-7) 7% 3-HH-O1 (3-1) 28%3-HHB-3 (4-1) 5% 3-HHB-O1 (4-1) 4% 3-HHEH-3 (—) 3% 3-HHEH-5 (—) 2%

NI=81.1° C.; Tc≦−20° C.; Δn=0.091; η=19.8 mPa·s; Δ∈=−3.0; Vth=2.30 V.

Example 8

3-HB(F)HH-5 (1-1-3) 9% V-HB(2F,3F)-O2 (2-1) 14% V-HB(2F,3F)-O4 (2-1) 14%2-HBB(2F,3F)-O2 (2-7) 6% 3-HBB(2F,3F)-O2 (2-7) 11% 5-HBB(2F,3F)-O2 (2-7)7% 2-HH-3 (3-1) 28% 3-HHB-3 (4-1) 3% 3-HHB-O1 (4-1) 3% 3-HHEH-3 (—) 3%3-HHEH-5 (—) 2%

NI=79.7° C.; Tc≦−20° C.; Δn=0.091; η=17.2 mPa·s; Δ∈=−2.8; Vth=2.27 V.

Example 9

3-HB(F)HH-5 (1-1-3) 5% 3-HB(2F,3F)-O2 (2-1) 4% 5-HB(2F,3F)-O2 (2-1) 12%1V2-HB(2F,3F)-O2 (2-1) 14% 2-HHB(2F,3F)-1 (2-4) 11% 3-HHB(2F,3F)-1 (2-4)11% 3-HHB(2F,3F)-O2 (2-4) 11% 5-HHB(2F,3F)-O2 (2-4) 8% 3-HH-4 (3-1) 11%3-HH-5 (3-1) 6% 3-HB-O2 (3-2) 7%

NI=82.5° C.; Tc≦−30° C.; Δn=0.083; η=21.7 mPa·s; Δ∈=−3.2; Vth=2.24 V.

Example 10

3-HB(F)HH-5 (1-1-3) 4% 5-HB(2F)HH-V (1-2) 4% 3-H2B(2F,3F)-O2 (2-2) 18%5-H2B(2F,3F)-O2 (2-2) 16% V-HHB(2F,3F)-O2 (2-4) 4% V-HHB(2F,3F)-O4 (2-4)4% 3-HH1OB(2F,3F)-O2 (2-6) 5% 4-HH1OB(2F,3F)-O2 (2-6) 4% 3-HBB(2F,3F)-O2(2-7) 10% 5-HBB(2F,3F)-O2 (2-7) 3% 2-HH-3 (3-1) 20% 3-HHB-1 (4-1) 5%3-HHB-O1 (4-1) 3%

NI=83.7° C.; Tc≦−20° C.; Δn=0.089; η=21.7 mPa·s; Δ∈=−3.6; Vth=2.28 V.

Example 11

3-HB(F)HH-5 (1-1-3) 4% 3-H2B(2F,3F)-O2 (2-2) 20% 5-H2B(2F,3F)-O2 (2-2)20% 3-HH2B(2F,3F)-O2 (2-5) 10% 5-HH2B(2F,3F)-O2 (2-5) 10%3-HBB(2F,3F)-O2 (2-7) 8% 5-HBB(2F,3F)-O2 (2-7) 8% 3-HH-V (3-1) 6%V2-BB-1 (3-3) 4% 2-BB(F)B-3 (4-3) 10%

NI=82.6° C.; Tc≦−30° C.; Δn=0.120; η=23.6 mPa·s; Δ∈=∈4.2; Vth=2.01 V.

Example 12

V-HB(F)HH-5 (1-1-1) 5% 3-HB(F)HH-5 (1-1-3) 5% V-HB(2F,3F)-O2 (2-1) 15%3-H1OB(2F,3F)-O2 (2-3) 10% 3-HHB(2F,3F)-O2 (2-4) 3% 2-HBB(2F,3F)-O2(2-7) 5% 3-HBB(2F,3F)-O2 (2-7) 8% 5-HBB(2F,3F)-O2 (2-7) 7% 2-HH-3 (3-1)5% 3-HH-O1 (3-1) 16% 3-HHB-3 (4-1) 5% 3-HHB-O1 (4-1) 4% 5-HBB-2 (4-2) 3%1-BB(F)B-2V (4-3) 2% 3-HHEH-3 (—) 3% 1O1-HBBH-5 (—) 2% 4-HHEBH-5 (—) 2%

NI=91.2° C.; Tc≦−20° C.; Δn=0.102; η=22.9 mPa·s; Δ∈=−3.5; Vth=2.29 V.

The liquid crystal composition that satisfies at least one ofcharacteristics such as a high maximum temperature of a nematic phase, alow minimum temperature of a nematic phase, a small viscosity, asuitable optical anisotropy, a negatively large dielectric anisotropy, alarge specific resistance, a high stability to ultraviolet light, and ahigh stability to heat, or that is suitably balanced regarding at leasttwo characteristics thereof. The liquid crystal display devicescontaining the composition are desirable for an AM device having a shortresponse time, a large voltage holding ratio, a large contrast ratio, along service life and so forth, and can be used for a liquid crystalprojector, a liquid crystal television and so forth.

What is claimed is:
 1. The invention concerns a liquid crystalcomposition having a negative dielectric anisotropy that includes twocomponents, wherein the first component is at least one compoundselected from the group of compounds represented by formulas (1), thesecond component is at least one compound selected from the group ofcompounds represented by formulas (2):

wherein R¹, R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine; R³ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons; one of X¹ and X² is oxygenand the other is fluorine; ring A is independently 1,4-cyclohexylene or1,4-phenylene, arbitrary one —CH₂— in 1,4-cyclohexylene may be replacedby —O—; Z¹ is independently a single bond, ethylene, methyleneoxy orcarbonyloxy; and m is 1 or
 2. 2. The liquid crystal compositionaccording to claim 1, wherein the ratio of the first component is fromapproximately 5% by weight to approximately 30% by weight, and the ratioof the second component is from approximately 30% by weight toapproximately 95% by weight, based on the total weight of liquid crystalcomposition.
 3. The liquid crystal composition according to claim 1,that in addition to a first, a second component, further includes atleast one compound selected from the group of compounds represented byformula (3) as a third component:

wherein R⁵ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁶ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; ring B andring C are each independently 1,4-cyclohexylene or 1,4-phenylene; Z² isa single bond, ethylene, methyleneoxy or carbonyloxy.
 4. The liquidcrystal composition according to claim 3, wherein the first component isat least one compound selected from the group of compounds representedby formula (1-1):

wherein R¹ and R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine.
 5. In the above formula (1-1) of the first component, theliquid crystal composition according to claim 4, wherein at least one ofR¹ and R² is one compound selected from the group of compoundsrepresented by alkenyl having 2 to 12 carbons.
 6. The liquid crystalcomposition according to claim 3, wherein the second component is atleast one compound selected from the group of compounds represented byformula (2-1) to (2-7):

wherein R³ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons.
 7. The liquid crystalcomposition according to claim 3, wherein the third component is atleast one compound selected from the group of compounds represented byformula (3-1) to (3-3):

wherein R⁵ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁶ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.
 8. Theliquid crystal composition according to claim 7, wherein the thirdcomponent is at least one compound selected from the group of compoundsrepresented by formula (3-1).
 9. The liquid crystal compositionaccording to claim 3, wherein the first component is at least onecompound selected from the group of compounds represented by formula(1-1), the second component is at least one compound selected from thegroup of compounds represented by formula (2-1) to (2-7), and the thirdcomponent is at least one compound selected from the group of compoundsrepresented by formula (3-1):

wherein R¹ and R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine; R³ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons; R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons; R⁵ is alkyl having 1 to 12carbons, alkenyl having 2 to 12 carbons; R⁶ is alkyl having 1 to 12carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons,or alkenyl having 2 to 12 carbons in which arbitrary hydrogen isreplaced by fluorine.
 10. The liquid crystal composition according toclaim 3, wherein a ratio of the first component is from 5% by weight to30% by weight, a ratio of the second component is from 30% by weight to80% by weight, and a ratio of the third component is from 5% by weightto 50% by weight, based on the total weight of the liquid crystalcomposition.
 11. The liquid crystal composition according to claim 3,that in addition to a first, second, and third component and furtherincludes at least one compound selected from the group of compoundsrepresented by formula (4) as a fourth component:

wherein R⁷ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁸ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons; ring D and ring E are eachindependently 1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenyleneor 2,5-difluoro-1,4-phenylene; Z³ is a single bond, ethylene,methyleneoxy or carbonyloxy.
 12. The liquid crystal compositionaccording to claim 11, wherein the fourth component is at least onecompound selected from the group of compounds represented by the formula(4-1) to (4-3):

wherein R⁷ is alkyl having 1 to 12 carbons, alkenyl having 2 to 12carbons; R⁸ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, or alkenyl having 2 to 12 carbons.
 13. The liquid crystalcomposition according to claim 12, wherein the fourth component is atleast one compound selected from the group of compounds represented bythe formula (4-1).
 14. The liquid crystal composition according to claim11, wherein a ratio of the fourth component is from 5% by weight to 30%by weight, based on the total weight of the liquid crystal composition.15. The liquid crystal composition according to claim 1, wherein thecomposition has a maximum temperature of a nematic phase of 70° C. ormore, an optical anisotropy (25° C.) at a wavelength of 589 nm of 0.08or more, and a dielectric anisotropy (25° C.) at a frequency of 1 kHz of−2 or less.
 16. A liquid crystal device display that includes the liquidcrystal composition according to claim
 1. 17. The liquid crystalcomposition according to claim 16, wherein the liquid crystal displaydevice has an operation mode of a VA mode, an IPS mode or a PSA mode,and has a driving mode of an active matrix mode.